Sewer systems in the United States are typically constructed of sections of plastic, tile or cement pipe connected and bedded below the ground surface for the transmission and directional flow of waste water. Access to this system is achieved by precast sections of large diameter concrete pipe manufactured in various standard heights and stacked atop one another so any desired distance from ground level of the live sewer can be obtained for inspection or maintenance. This is commonly called a manhole. Once the sections of the manhole are placed and bedded with compacted sand, gravel or loam material, a metal casting and a cover lid, with standard dimensions is set in place so that it inner fits with the precast riser rings of the manhole. This casting assembly is engineered and installed so that it is flush or even with the roadway. This casting assembly is commonly referred to as a manhole cover. Due to varying surface conditions and the changing elevation found necessary to arrive at an engineered percent of fall for natural flow, the casting assembly is positioned above the flow line at predetermined elevations. The precast riser rings mentioned in line eighteen of page one can presently be obtained in heights of two, three or six inch variations to achieve an approximate finished elevation at the manhole cover. However, exact finish elevation can not be achieved by this precast product. Therefore it is common in the construction industry to use small cement or steel blocks to temporarily position the manhole casting at the desired elevation above the precast riser rings and mixed cement is poured into the void created by the blocks. In the past, to avoid uncontainable cement from falling into the sewer system a wooden form is constructed and placed inside the riser rings. Many times no form at all is used. With this method the cement is mixed very stiff and pushed into the void by hand and can not withstand much vibration which increases the density and the eventual strength of the concrete.
Another common situation requiring the relocation of a manhole casting assembly is when a asphalt roadway needs to be paved again or as the industry calls it "overlaid". All manholes must be chipped out with jackhammers and raised up as much as ten inches to match and be flush with the new pavement. If the road bed needs to be leveled or a change in the grade is required, the manholes castings finish elevations may need to be decreased or lowered. Sometimes a fraction of an inch is necessary for arriving at proper finished elevation and the precast riser rings are ineffective.
Although the desirability of being able to have a lightweight, reusable form that can be easily installed and expanded to contain vibrated cement for this procedure, no one has been able to provide a suitable apparatus with an instantaneous locking feature for this specialized forming operation. This invention allows a handicapped individual with limited knowledge and strength or a person with one arm to accomplish the forming operation. Alternatives to this concept of a standardized collapsible unit is a costly and time consuming process to perform this task. These methods include thin strips of plywood or metal curved and formed to the shape of the inside of the manhole and held in place by a plurality of nails and braces, which if not properly installed can fall and risk plugging a sewer pipe. Known designs are generally for large diameter applications and require extra tools to facilitate their use and equipment to place a form in position.
In addition the present invention is intended to assist with the alignment of the metal casting assembly with the riser rings, thereby performing another useful function. As well, this invention shall not be limited to the relocation of manholes, but upon their initial installation.